Since the mid-20th century, intraocular lenses (IOLs) have been implanted in eyes, replacing a patient's natural crystalline lens that is clouded by cataracts or changing the eye's optical power. Initially, IOLs were fixed monofocal lenses of a power to provide correction only for distance vision. Even today, a majority of IOLs implanted during eye surgery are monofocal, requiring a patient to wear glasses for near vision correction.
More recent advances have included multifocal IOLs which provide a patient with correction for both distance and near vision. Multifocal IOLs employ the same technology as multifocal contact lenses, but implemented within an intraocular lens.
Some IOLs currently claim adaptive capabilities, providing the patient with limited visual accommodation. Accommodating IOLs are designed to allow the eye to shift focus onto near objects. Current versions of accommodating IOLs rely on physical changes within the eye to effect a change in the shape of an intraocular lens, resulting in a change in the lens' optical power. In many implementations, the optical properties of accommodating IOLs cannot be changed after implantation, although such changes may be desirable for a variety of reasons. In many cases, a patient's vision prescription changes as a result of the eye surgery necessary to implant the IOL. The closure and healing of the incision may induce astigmatism as portions of the eye are drawn together to close the incision. Further, as a patient ages and ciliary muscles within the eyes weaken, the eyes are no longer able to exert the necessary force to change an IOL's shape and achieve the desired level of accommodation. Finally, even a minor error in the initial IOL prescription will leave the patient with less than optimal vision.
More recently, it has been theorized that electronic components may be incorporated into an intraocular lens. Electronic components may enable an intraocular lens including a liquid meniscus lens which provides variable focus that can be controlled and adjusted in a variety of ways.